Kinases are responsible for the control of a wide variety of signal transduction processes by phosphorylation of their target proteins. Kinases regulated processes include proliferation, growth, differentiation, metabolism, cell cycle events, apoptosis, motility, transcription, and translation. Kinases can function, either directly or indirectly, to activate, inactivate, or modulate the activity of the target protein. These target proteins may include, for example, metabolic enzymes, regulatory proteins, receptors, cytoskeletal proteins, ion channels or pumps, or transcription factors.
Polo-like kinases (PLKs including PLK1, PLK2, PLK3 and PLK4) are serine/threonine protein kinases that are involved in the regulation of the cell cycle. In mammalian cells, PLK1 levels increase during mitosis. Target proteins for PLKs include cyclin B, a cohesin subunit of the mitotic spindle, subunits of the anaphase promoting complex, and mammalian kinesin-like protein 1 and other motor proteins. PLK1 has a role in the regulation of CDKs through phosphorylation and activation of Cdc25C leading to activation of CDK1 which is involved in cell division processes. 4-(9-Cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-ylamino)-3-methoxy-N-(1-methylpiperidin-4-yl)benzamide is an inhibitor of PLKs, particularly PLK1.